Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol 1: A-Dea
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25759/590/
678 
CETACEA. 
The disappearance of the posterior members 
has occasioned that of the vessels which should 
nourish those members ; and as the tail has 
attained a considerable development, the arte¬ 
ries and veins which belong to this last part of 
the trunk have been developed in the same 
proportion. The abdominal aorta does not 
send off any external iliacs, but is continued 
underneath the tail in the canal of the inferior 
processes, from whence its ramifications are dis¬ 
tributed to the muscles which move this organ. 
The modifications of the venous system are in 
many respects analogous to those of the arteries. 
Fig. 266. 
The quantity of blood contained in the vascu¬ 
lar system appears to be proportionally much 
greater than in the other Mammalia. 
[In the Porpesse the veins are almost univer¬ 
sally devoid of valves, so that they can be as 
easily injected from trunks to branches, as in 
the reverse direction. The plexiform disposi¬ 
tion which we have seen to characterize so 
many parts of the arterial system is still more 
strongly displayed in the venous. Thus in the 
system of the anterior vena cava, with the ex¬ 
ception of the trunk of that vein itself, and the 
short jugular veins which join it, an internal 
and an external j ugular branch, and a pair of 
large subcutaneous veins, all the other parts of 
the system manifest the plexiform 
disposition. This is most remark¬ 
able in the large venous sinuses 
surrounding the central axis of the 
nervous system, which receives the 
intercostal veins, and by means of 
which the system of the anterior 
cava is chiefly brought into com¬ 
munication with that of the pos¬ 
terior cava; for, as V. Baer has 
observed, there is no intercommu¬ 
nicating channel analogous to the 
vena azygos of the higher Mam¬ 
malia. 
Of the venous plexuses belong¬ 
ing to the system of the inferior 
cava, that which is found at the 
posterior parietes of the abdominal 
cavity extending from below the 
kidney to the lower boundary of 
the abdomen is the most remark¬ 
able, and we have selected in 
illustration of this, the figure from 
Baer’s excellent memoir on the vas¬ 
cular system of the Cetacea.* In 
this figure (fig. 266) the anterior 
parietes of the abdomen are remo¬ 
ved. The two immense lateral de¬ 
pressor muscles of the tail are seen 
at A, A, and B shows their point 
of convergence to be inserted into 
the inferior spinous processes, by 
which the cavity of the abdomen is 
contracted and defined posteriorly. 
Just anterior to this commissure 
is seen the termination of the rec¬ 
tum H. C, C, are the two ischia. 
D, D, the posterior parietes of the 
chest projecting forwards over the 
abdomen. On the right side the 
kidney and the peritoneum are re¬ 
moved; on the left side they are 
seen in situ, and also a part of the 
left cornu of the uterus G, with 
the oviduct and ovary K. 
At p is seen the inferior vena 
cava cut through, which lies in the 
interspace of the two great depres¬ 
sors of the tail. The trunk of the 
smaller than it 
vena cava seems 
Abdominal venous plexus and kidney of the Porpesse. 
* Ueber das Gefass - system des 
Braunfisches, Nova Acta, Phys. Med. 
Leopold. Carol, tom. xvii. 1Ö35.
        

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